Psak Halacha from the Posek HaDor, the great Gaon, the Rav Av Beis Din of Yerushalayim shlit"a: Informers may not be counted toward a minyan!!
Today, at the opening-of-the-zman address in the hall of his yeshiva, the Rav Av Beis Din addressed the informers who give testimony to the police in the current crackdown regarding talmud Torahs and yeshivas that are open, as well as weddings taking place in violation of the law.
The Posek HaDor said, "According to halacha, such people may not be counted toward a minyan."